Electrical spark gap



April 23, 1940. R. N. SAXBY 2,198,062

ELECTRICAL SPARK GAP Filed Sept. 25. 1937 INVENTOR ROBERT NORMAN SAXBY %4 'ATTY Patented Apr. 23, 1940 UNITED STAES ELECTRICAL SPARK GAP ware Application September 25, 1937, Serial No. 165,618 In Great Britain October 12, 1936 2 I Claims.

The present invention relates to electrical spark gaps and is more particularly concerned with the construction of enclosed spark gaps of the mercury type. Such arrangements find advantageous application in high-frequency generating apparatus which may be used, for example, for the remote control of street lighting in themanner disclosed in British specification No. 435,564.

In one form of such an arrangement the container is a glass bottle and the electrodes consist of two steel rods, one of which dips into a bath of mercury whilst the other is adjustable to a position adjacent to the surface of the mercury. The container is preferably filled with hydrogen at substantially atmospheric pressure when the gap is not in operation. Adjustment of the spark gap is effected by sliding the movable electrode up or down through a rubber plug which is inserted in the neck of the bottle and which serves as a sealing means.

In practice however, it has been found that with the above described method of gap adjustment, there is a tendency for air to leak into the container with deleterious effects on the efficiency and life of the arrangement. The chief object of the invention is therefore to overcome this difficulty by the provision of improved sealing arrangements which still permit simple and accurate adjustment of the gap.v

According to the invention in an electrical spark gap of the mercury type for use in high frequency generating equipment the sparking chamber is hermetically sealed and adjustment of the length of the gap is effected by movement of the container.

The invention will be better understood from the following description of one method of carrying it into effect, reference beinghad to the accompanying drawing.

It will be seen that the arrangement comprises a substantially spherical container l0 preferably of glass into which are sealed at opposite poles two metal rods H and [2, preferably of iron, which form the two electrodes. The lower one I2 makes contact with a pool of mercury IS in the bottom of the sphere while the upper electrode ll terminates at its'inner end in a pendulum M with its pivot point !5 displaced somewhat from the centre of the sphere. The whole arrangement is filled with hydrogen or other suitable gas at substantially atmospheric pressure and is finally sealed at the point l8.

Adjustment of the spark gap is effected by tilt-e allel, thus maintaining the current-carrying capacity at a constant'maxi mum level.

In an alternative form of construction the container would preferably be cylindrical rather than spherical and the pendulum arrangement would be dispensed with and the electrodes given fixed positions. Adjustment of the gap would be made in this case by increasing or decreasing the amount of mercury in the pool from a separate supply. This could be carried in a troughshaped gallery encircling the inside upper part of the container or in a small auxiliary cham her, the neck of which is sealed round a small hole provided in the vertical wall of the contamer. By suitably shaking or momentarily tilting the container mercury can be transferred from the reservoir into the main electrode pool or vice versa and the level adjacent the free electrode thus adjusted.

Iclaim:

l. A two-electrode electrical spark gap comprising a spherical envelope adapted to rotate through a certain are around a horizontal axis, conductors sealed through different points of said envelope, one electrode comprising a pool of mercury in the envelope with one of said conductors shaped to maintain contact therewith during said rotation, the other of said COnduC-1 tors shaped to form a support eccentric to the envelope for the other electrode, said other electrode comprising a pendulum, having a wide, flat surface parallel to the mercury surface, pivotally mounted on said support, said surface thereof retained in parallel relation to the free surface of the mercury throughout said rotation.

2. An adjustable electrical spark gap having two electrodes within 'a suitable envelope, one electrode comprising a pool of mercury, the other electrode having a wide, fiat surface adjacent the mercury, a pivot supporting said other electrode, said pivot supporting said second electrode in such a manner that it'swings freely from the pivot and thus maintains a parallel relation between said surface thereof and the free' surface of said mercury. I

ROBERT NORMAN SAIBY. 

